Set mention in notification

[unkoman]

Is your feature request related to a problem? Please describe.
Hi
I would like to add a mention such as channel when a workflow notification fails. #1563

Describe the solution you'd like
Adding this configuration likeworkflows:{event:"push", branch:"main", mention: "channel"}would be super useful.

Describe alternatives you've considered
I set slackapi/slack-github-action in the workflow of all repositories I manage.

Additional context
I would be happy if the workflow notification looked like this.
@channel Workflow was triggered via pull_request by unkoman